No. In fact you are more likely to find a comma before both those words. 2) In that context 'to this matter' is correct as 'to' collocates with 'time you've devoted'. On/in this matter are possibilities in other contexts. 3) It's not really less polite but it is much less formal.
Anxiety Causes. Problem anxiety may be caused by a mental condition, a physical condition, the effects of drugs, or from a combination of these. The doctor's initial task is to see if your anxiety is caused by a medical condition. Conditions as varied as anemia, asthma attack, infection, drug intoxication or withdrawal, or a number of heart conditions are just a few examples of medical problems that can be associated with anxiety.
Other anxiety disorders include obsessive-compulsive disorder and post-traumatic stress disorder (PTSD). Because they so often go hand in hand, anxiety and depression are considered the fraternal twins of mood disorders. Believed to be caused in part by a malfunction of brain chemistry, generalized anxiety is not the normal apprehension one feels before taking a test or awaiting the outcome of a biopsy.